Horizontal gene transfer allowed the emergence of broad host range entomopathogens

Abstract

Significance Recently emerged fungal diseases are contributing toward global declines in wildlife, but the mechanisms for emergence of new pathogenic fungi remain mysterious. The entomopathogen Metarhizium robertsii evolved from plant symbionts, and here we report that this host shift was facilitated by 18 horizontal gene transfers (HGTs). The necessity of breaching cuticular barriers selected for retention of these genes, as 12 are up-regulated during penetration, and their collective actions are indispensable for infection by processes including degradation of procuticular proteins and utilization of epicuticular lipids. Five of the most recently acquired HGT genes contributed to host-range expansion in some late-evolving species. Our work reveals that HGT was a key mechanism for emergence and host-range expansion of fungal entomopathogens.